Selective signaling system



` June 1l, 1935. w H T, HOLDEN 2,004,244

SELECTIVE SIGNALING SYSTEM Filed Deo. 14, 1934 2 Sheets-Sheet 1 Cord Ckt.

INVENTOR WZZTHoZdeZn/ ATTORNEY June l1, 1935. W, H T HOLDEN SELECTIVE SIGNALING SYSTEM Filed Deo. 14, 1934 2 Sheets-Sheet 2 INVENTOR WEZHoZde/m ATTORNEY 9 l Ill IMM.

Patented June 11, 1935 i, UNiTEDsTATE-s PATENroi-FICE William Henry Towne Holden, Brooklyn, N. Y., assigner to.American Telephone and Telegraph i or "control gap.

Company, a corporation of New York Application December 14, 1934, Serial No. 757,517 4 ciaims. (C1. 17a-86)'y This Vinvention relates to electricalcircuits and more particularly to that class of circuits used for Aselective ringing or signaling, whereby a signal may be operated at one of a plurality vof stations connected to the same line.

In the past it has been usualto obtain selective ringing by suitable connections vbetween line and ground, together with the `useof bias arrangements, as in the well known four-party selective ringing system. The arrangements there used are inherently limited to not more than four stations. Where greater numbers ofwstations are required it .has been necessary to resort to harmonic ringing, selectors at stations, or other expedients. 1 l It is `one of the objects of this invention to provide a selective-ringing system which will permit-full selective operation up to eight stations, without requiring multi-frequency generators to be used. l Y 4 Another object is to provide a fully selective system which will be distinguished from semiselective systems. In otherwords, one ofthe objects of this invention is to signal any one of a plurality of different stations independently of all of the remaining stations. Thus, in an eightparty system,` for example, one ofthe parties would be exclusively signaled while all of the remaining parties would be absolutely unaware that the single party was so signaled. i Other `objects of this invention `will be apparent from Vthe following description when read in connection with the accompanying drawings in which certainembodiments of the invention are illustrated.

Referring to the drawings, Figure l is a `dia-v grammatic illustration of one modiiication of the invention, showing biasing batteries at the sev-V eralstations connected with 'the line circuit, and Fig. 2` is a modification thereof are substituted for said batteries.-

The means utilized at the stations for produc-- ing the selective operation include a cold electrode gas lled discharge tube, of the type commonly referredto in the art as a cold cathode ionic tube of the double gap type. Such tubes possess a cathode, coatedpreferably with some material to reduce the cathode fall, or activated, as this is termed, an auxiliary electrodaialso activated, and so spaced fromthe cathode thatthe breakdown voltage between this electrode and the cathode is relatively low, of the order of volts.' This discharge path, auxiliary electrode to cath-` ode, is spoken of as the control discharge path `These tubes are also provided withA an anode, `so spaced from the V"cathode that ode.

wherein rectiers the breakdown Voltage therebetween is much greater-than that from cathode to auxiliary electrede, and voltages of 200 to`300 are typical. The minimum voltage to sustain a discharge, once started, will be nearly the same for the two discharge paths, the main gap,or anode to cathode path `beingpossibly 10 volts higher. It is found that if a voltage less than the breakdown, but above the sustaining voltage is applied to the main gap, and a discharge is caused to pass through the controlgap, a breakdown of the mainr gap will take place, being triggered oli bythe] control gap. The main gap, that is, the gap` between the anode and one of the cathodes, can be broken down only when positively poled super-4 posed ringing current, hereinabove called a posi itive ringing current-is `applied between the anode 'and cathode. This `.main gap cannot be broken down when negative ringing current is applied to the anode. When positive ringing cur rent is thus applied to the anode and this current passes between said anode and the cathode, current is discharged through this path only during one-half cycle. During the remaining half of the cycle there` is no discharge whatever between the `anode and cathode. In other words, the tube acts as allait-'waveV rectierin that part of the tubewhich includes the anode and cath- Before aI particular'station can be effectively signaled, however, itis necessary that the controlgap and the main `gap be both broken down at `the station to be signaled.

Referring to Fig..l of the drawings, reference characters I, 2, `3, 4, 5, 6,.1 and 8 indicate subscrib'ers" stations, while I', 2', 32.4', 5', 6', l', and 8 indicate respective ringing keys at the central oliice.V When key 68 is operated so as to connect conductors 25 and 26 to conductors 2'! and 28,

respectively, and when key l is depressed, sta? `29 and 30 are the conductors constituting the metallic subscribers loop, across which the sub# scribers stations l Ato 8 are bridged. It may be remarked that only the ringing equipment has been shown in the drawings, as this invention is not concerned with the features of the talking circuit and the telephone instruments have therefore not been shown, in order to simplify the drawings.

When key I is depressed, conductor 25 is connected to conductor I9, through the upper contacts of key I', while conductor 26 is connected to conductor 2Q, through the lower'contacts of the same key. Conductor I3 is connected to the secondary of transformer I8, the other end of which is connected to ground through battery II. The primary transformer I is connected to ringing generator it, which supplies ringing current at a frequency of approximately 20 cycles per second. The voltages Vare so adjusted that the battery II will be approximately equal to the peak value of the 20V-cycle voltage in the secondary of transformer I8. This pulsating or superposed ringing current is therefore transmitted over conductor 25 through key 68, conductor 21, conductor 29 to all subscribers stations At all stations the voltage thereby applied is too low to break down the main Ydischarge path from anode to cathode in any of the cold cathode ionic tubes 32, 37, 42, 4G, 53, 55, 6I or 66, if no current is flowing in the control discharge paths thereof or from electrode to cathode. But the voltage of the negative battery I2, whose positive terminal is grounded, will be applied to conductor 3D, over conductor 20 and the lower contacts of key I', conductor 26, key 58, conducto-r 28 and conductor 30. Conductor 3E is connected to the control discharge gaps of tubes 32, 3l, 42, 4E, 6I and 56. No discharge will take place in tube 3l because the polarity of battery 4E, connected between cathode and ground, is such as to make the voltage across the control gap of tube 3'I too 10W to cause a discharge. The control gaps in tubes 42 and 43 are connected across the loop, and will therefore pass discharges, due to the total voltage difference between conductors I9 and 20, but the ringers at these stations are connected between the anode of the discharge tube and ground, and owing to the polarity of battery II, and rectifying property of the anode tov cathode circuit of these tubes, insufiicient current will flow to operate the ringers at stations 3 and 4. The same situation exists at stations 'I and 8. At station I, however, the polarity of battery 35 is such that it aids battery I2 to produce a discharge in the control gap of the ionic tube 32, the current i'iow being limited by resistances SI and 33. Whenever the anode of tube 32 is more than 65 to 19 volts positive, current will flow in the anode and cathode path, charging condenser 34. vWhen-ever the anodeV is less than 65 to 70 volts positive, condenser 34 will discharge through resistance 33 and battery 35. As a result pulses of current, corresponding to one-halt Wave rectied 20-cycle ringing current, will flow through the ringer at station I and give a signal at that station. Ringers at stations 5 and 6 cannot operate as they are not connected to the line conductor 2S.

If it is desired to signal station 2, key 2' is operated, instead of key I. As before, alternating ringing voltage superposed on the positive battery II is connected to conductor 25 and thence through key 63 to conductors 2l and 29, the circuit being completed over conductor I9, conductor Isa and the upper contacts of key 2'. As before, positive superposed ringing current ,applied to conductor V23 cannot cause ringer operation at stations 3, 4, 'I or 8 even if the control gaps of the tubes 42, 46, 6I, 66 at these stations break down, owing to the unilateral conductivity of the anode-cathode discharge paths of the ionic tubes employed. Ringers at stations 5 and 6 cannot operate as these ringers are not connected to the line conductor 29. The control gap in tube 32 at station I will not break down, as the operation of key 2' connected positive battery I3 over conductor 2! through the lower contacts of key 2 and conductor 23, through key 68 to conductors 28 and 30. The negative terminal of battery'I3 is grounded. This battery will oppose battery 35 at station I, but will aid battery 4D at station 2. The control gap of tube 3'I will pass a discharge and ringing current will as before ow through ringer at station 2, tube 31 and condenser 39 to ground, operating the ringing signal at station 2.

In a similar manner selective ringing of stations 5 or 6 may be obtained by depressing keys 5 or 6', the circuits being identical with those already described, except that ringing current is sent out over conductor 30 and negative battery over conductor 2S for station 5 from battery I2 and conductor 2B, and positive battery for station G from battery I3 over conductor 2l, there being no other difference beyond this interchange of functions of the conductors 29 and 30.

If it is desired to signal station 3, key 3 is depressed. 'Ihis connects conductor 22 to conductor 25 and thence through key 68 to conductors 2'I and 29. Conductor 22 is connected to one end of the secondary of transformer II, the other terminal of which is connected to ground through battery I4, whose positive terminal is grounded. The primary of transformer I'I is connected in parallel with that of transformer I8 to the source of ringing current l0. The voltages in this circuit are also so adjusted that battery I4 is substantially equal to the peak voltage in the secondary of transformer I'I, but as this battery is poled oppositely tobattery II, negative superposed ringing current is applied to conductor 29. This cannot operate ringers I or 2 even though the control gaps in these tubes break down, owing to the unilateral conductivity of the anode circuits. `Nor can it operate ringers 'I and 8 as the resistances 62 and 61 are too high to permit sufficient current to pass; while flow of ringing current through condensers 59 or 63 over conductor 30 back to key 3', conductor 32, and battery I5 is prevented by the large inductive reactance presented by inductance 69. Ringing current can only flow in sulicient quantity to operate a ringer through the ringers at stations 3, -or 4, depending upon which of the tubes 42 or 45 is caused to pass current by a discharge across the control gap thereof. The operation of key 3 connects battery I5 between conductors 25 and 23, the negative terminal thereof being connected to conductor 22 and thence to conductor 25 through the upper contacts of keyY 3', while the positive terminal of batteryY I5 is connected to conductor 23 through inductance 69, and conductor 23 is connected to conductor 25 through the lower contacts of key 3. The control gaps of tubes 42 and 43 are connected across conductors 29 and 30, which are connected respectively to conductors 25 and 25, via conductors 2l and 28 and key 68. Battery 43a. is so poled as to aid battery I5 in producing a discharge in the control gap of tube 42, while battery 41a. is poled in the reverse direction. Tube 42 will therefore pass a discharge in the control gap and ringing current will flow through condenser 44, main discharge path of tube 42, and,ringer to ground, operating the ringer at station 3. Had key 4 instead of 3 been operated, battery I6 would have been substituted for battery I5, and as this battery is poled oppositely, a discharge would have occurred in tubel instead of tube 42, and ringer atstation 4 would have operated instead of the ringer at station 3. In a similar mannerstations 'I or 8 could be signaled instead of 3 or 4, by oper.- ating the keys l" or 8. In this case negative superposed ringing current would be applied to conductor 30 instead of conductor29 and control battery I5 `or I5 would be applied between conductors 29 and 34 as before. The operation of the ringers at stations 3 or 4' will be prevented, although the control gaps in tubes 42 or 446 will break down, because there is no ringing current path of sufliciently low impedance to permit operation of ringers at stations3v or 4, owing to the high Value of resistances 4| `or 45 and the high inductive reactance of choke coils 'II or 72. It

will thus be seen that this system provides full selective eight-party ringing over'a metallic loop. Fig. 2 shows a inodication of the invention disclosed in Fig. l whereby the biasing batteries 35, 4t, 43a., 41a, 52, 5?, Slic; or 65 shown in Fig. 1 may be eliminated, the necessary direct voltages being obtained from the alternating ringing current by means of rectiers, preferablyof the copper-cuprous oxide or similar types. Referring to FigpZ reference characters?!` and 23 refer to the same conductors as shown in Fig. l., connected through the key 68 to the ringing keys I to 8', inclusive.: ,y Y W Conductors 27 and 28 are connected to the con.` ductors I0! and H32, respectively, of the subscribers loop through the switchboard in the well known manner. The details of this circuit are not shown, as not being essential to an understanding of this invention. As explained previously, when ringing key I is operated, positive superposed ringing current is sent out over conductor 2l to conductor IIiI, and negative battery is connected to conductor 28 and thence to conductor |52. Atstation I, positive superposed ringing current is applied to the anode of cold cathode ionic tube III! through'ringer at station I. At the same time the alternating component of the ringing current passes over conductor |53, from conductor IIlI to and through condenser |05 and to ground through the primary of transformer |56. The secondary of this transformer is connected to rectifier IBI which produces a Vdirect or pulsating direct potential across resistance |04,

in such a manner that the end of resistance |04,

connected to resistance IGS is positive while the end of resistance HB4 connected to the control electrode of tube IIE is negative. The battery connected to conductor |52 Vover conductor 28 as previously described is positive grounded, the negative side being connected to the circuit. The voltage across the control gap of tube I ID will thus be the sum of the two voltages, and this will be adjusted so as to be suncient to cause a discharge to pass in the control gap. As a result ringing current will flow in the main gap and ringer at station I will be operated.

The ringer at station II will not be operated under this condition because the rectier H5, supplied with alternating ringing current from the secondary of transformer II4, is poled oppositely and thus thevoltage on the control gap, being the diiference of potential between battery I2 and the output of rectiiier ||5 working resistance I I2 will be too low to cause a discharge to pass in the control gap. Noiringing current sulicient to cause a signal will `flow through tubes at stations III and IV, or VIIrand VIII because of the unilateral conductivity of the anode cathode discharge path of the ionic tubes.V No signals will occur at stations V or VI because, while, the ringing current may cause discharges in the control gap, the battery voltage on conductor H32 is too low to cause a discharge inthe main gapunder any conditions. Thus station I will be signaled i in a selective manner.

' |34 and |45 when the anodes are negative. Tubes |22, |23, |45 or |52 would be able to pass a ringing signal, but no sufficient current to operate lthe ringers can flow through the resistancesv I4I and |42 at station VII orwid'l and |48 at station VIII, nor through the reactance Se interposed 1n conductor 23 between key 3 and battery I 5. This will prevent operation of tubes or |52. In

addition, of the rectiflers MI5, I5,|, only |45 is so poled4 that the output thereof will aid battery I5 to produce a discharge in the control gap circuit. The presence of reactance 59` however prevents a falseisignal on the ringer at station VII when station III is desired. In the case of sta-` tion III, the A. C. component of ringing current flows from the conductor IilI through condenser rI I9 `to and through the *primary of transformer I 25 to ground. The secondary of this transformer is connectedto rectifier I2I, which applies a potential to resistance I I 8 of suchfpolarity as to., assist battery `I5in causing a discharge of the control gap of tube |22, which results then in a flow of negative superposed ringing current from conductor I5! through tube E22 and ringer at station III to ground, causing a signal at station III'.` yIn the case of station IV, the opposite poling of rectier |27 opposes battery I5 sothat the control gap of this tube does not break down and no Vsignal takes place at station IV. But if key 4 be operated instead of 3', battery I6, of opposite poling, is substituted for battery I5, and now theoutput of rectifier |2| opposes the battery voltage, while that of rectifier I 2'! aids it. Accordingly,a discharge passes in the control gap of tube |28, resulting in a flow of ringing current from conductor It! through tube I 28 and the ringer at station IV to ground. As a result, the ringer at station IV operates but not the ringer at station III. A discharge also occurs .in the control gap of tube |52 at station VIII, but reactance 10 limits the current to a value too small to operate the ringer at station VIII and hence only station IV is signaled.

Stations V, VI, VII and VIII are connected in a manner similar to I, II, III, and IV,` except that for the operation of the stations V, VI, VII and VIII, theringing current must be applied to conductor |02 and the control battery to conductor IDI, instead of vice versa, as for Vthe rst four stations I, II, III and IV. It thus appears that full selective signaling can be accomplished by the system shown in Fig. 2, which has the ad- Vantage of eliminating the station batteries shown in Fig. 1.

While this invention has been described with regard to certain specic embodiments thereof, it is to be understood that it is not so limited, but includes any and all arrangements falling within the scope and spirit of the appended claims.

What is claimed is:

1. In a signaling system, the combination of a plurality oi subscribers stations, a ringer at each subscribers station, a three-electrode gas-lled tube at each subscribers station, each gas-lled tube having two electrodes which form a control gap and an anode which together with one of the electrodes forms a main gap in series with which the corresponding ringer is connected, a loop across which all of the subscribers stations are connected, and means responsive to current received over said loop for simultaneously discharging t'ne control gap and the main gap of the gas-filled tube at a selected subscribers station to the exclusion of all other subscribers" stations so as to operate the ringer at said selected subscribers station. i

2. In a multi-party ringing system, the combination of a plurality of subscribers stations, a two-wire line across which all of the subscribers stations are connected, a source of alternating current, two sources of direct current, means for connecting said source of alternating current and one of said sources of direct current to one of the wires of said line and the other source of direct current to the other wire of said line, a three-electrode gas-lled tube at each subscribers station, each of which tubes has a control gap, and a main gap, and means including said sources of current for simultaneously discharging both gaps or the tube at a selected station, said sources of direct current being so poled that only one of said subscribers stations will be effectively signaled to the complete exclusion of all other subscribers stations.

3. In a multi-party Vsignaling system, the cornbination of a plurality of subscribers stations, a two-wire line across which all of the subscribers stations are connected, a source of alternating current, two sources of direct current, means for connecting said source of alternating current and one of said sources of direct current to one of the wires of said line and the other source of direct current to the other wire of said line, switching means for selectively controlling the polarity of both sources of direct current connected to the two wires of said line and for selectively controlling the connection of said source of alternating current to either of said wires of said line, a plurality of cold cathode three-element gas-filled tubes each of which has two electrodes which form a control gap and an anode which, together with one of said electrodes, forms a main gap, one of said tubes being located at each of said subscribers stations, and means at each of said stations responsive to the currents transmitted over the said two-wire line, said means including means for simultaneously discharging the control gap and the main gap of only one of said gaslled tubes to the exclusion of all other or" said tubes whereby the subscribers station at which both of the gaps of the said tubes have become discharged Will be signaled to the exclusion of all other subscribers stations.

4. In a multi-party signalingY system, the combination of a plurality of subscribers stations, a plurality of indicating devices, a plurality of three-element tubes each having two electrodes forming a control gap and an anode which, together with one of the electrodes, forms the main gap, a plurality of full wave rectiers at each subscribers station including means for interconnecting one of said indicating devices, one of said devices'and one of said rectiers so that the corresponding rectier will be in circuit with the control gap of said tube and the indicating device will be in, circuit with the main gap or" said tube, a two-wire line to which all of said subscribers stations are connected, a source of altere nating current, two sources of direct current, means vfor selectively connecting thesource or" alternating current and one of said sources or direct current to one of the wires and the other source of direct current to the other of the wires and for controlling the polarity of the sources of direct current so connected, the rectiiiers and the main gaps of the tubes at the various subscribers stations being so poled that only one of the indicating devices will be operated to the exclusion of all of the other indicating devices.

WILLIAM HENRY TOW NE HOLDEN. 

